1. Field of the Invention
The present invention relates to a method for packaging an LED, and in particular relates to the thermoplastic material utilized in this method.
2. Description of the Related Art
Epoxy resin and silicone are the most popular materials used when packaging a light-emitting diode (LED). Considering lower costs and electrical properties, epoxy resin is applied in vehicle illumination and traffic signal LED devices, and silicone is applied in high efficiency liquid crystal displays (LCDs). The epoxy resin belongs to the family of thermosetting material, however, the packaging method utilizing epoxy resin is a time consuming infusion molding or transfer molding packaging method. In addition, the epoxy resin has poor UV resistance and climate resistance, is easily yellowed, and is not recyclable. Compared to epoxy resin, a low cost polymethylmethacrylate (PMMA) material has excellent UV and climate resistance. However, the PMMA has lower Tg (about 100° C.) than the epoxy resin (about 130° C.), the PMMA has higher moisture absorption (2.0 wt %) than the epoxy resin (0.5 wt %), and the PMMA has lower refractive index (1.49) than the epoxy resin (1.54). Accordingly, a novel thermoplastic material with mainly the advantages of both the low cost PMMA material and the epoxy resin for packaging an LED is called for.